Thermal switch



21, 1961 w. c. MOODIE, JR, ET AL 2,972,665

THERMAL SWITCH Filed Dec. 14, 1959 FIG.

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\\\\ 5, Maw/E J f ATTORNEY United States Patent THERMAL SWITCH William C. Moodie, Jr., Montclair, and Edward B. Hildum, Plainfield, N.J., assignorsto Control Products Inc., Harrison, NJ., a corporation of New Jersey Filed Dec. 14, 1959, Ser. No. 859,491

7 Claims. (Cl. 200-138) This invention relates to a thermal switch and more particularly such switch to be moved into the recess of an article whose temperature changes are to be signalled by actuation of the switch. This invention has particular reference to a switch of relatively small dimensions; one of the problems heretofore encountered has been the designing of such switches so that they will be constantly in direct and positive contact with the article on assembly and in use.

The switch of the invention is formed two parts--an outer casing which is moved into the recess of the article and an inner shell slidably disposed in the casing and urged by spring means in one direction. The inner shell has a heat absorbing head secured to one end thereof and means engage the shell and casing to urge the heat absorbing head of the shell out of the casing. Thus on threading the casing to the article, the heat absorbing head of the inner shell will be held against the inner end of the recess of the article on further threading the casing into the recess, said shell will retract within the casing against the tension of the spring which thus continues with more force to urge the heat absorbing head into constant positive contact with the inner end of the article recess.

The invention has particular reference to switches to be actuated responsive to thermal conditions or changes for example, to actuate a warning light or other signal or to open a circuit or otherwise indicate a condition or change in thermal conditions.

The drawings, illustrating procedures and devices use ful in carrying out the invention, and the description below, are exemplary only of the invention, which shall be deemed to cover all other devices and procedures coming within the scope and purview of the appended claims.

In the drawings, wherein similar reference characters indicate like parts:

Fig. l is an enlarged longitudinal sectional view of a switch embodying the invention, shown inserted in the threaded recess of an article,

Fig. 2 is a longitudinal, elevational view thereof,

Fig. 3 is a partly fragmentary view similar to Fig. 1, showing the inner shell of the switch and part of one end of the outer casing in elevation, and

Fig. 4 is a fragmentary longitudinal sectional view of a normally closed switch embodying the invention.

As shown in the drawings, illustrating a preferred form of the invention, the switch of this invention comprises an outer casing 11 to be secured to the threaded recess 12 of an article 13 whose changes in temperature actuate the switch either from normally open (Fig. 1) to normally closed or from normally closed (Fig. 4) to normally open position. The recess 12 of the article 13 has an inner end 14 and extends inwardly of the outer surface 15 of article 13. The outer casting 11 of the switch is open at one end 16 and has an axial internal opening 17 extending to said open end 16 thereof. The casing 11 is externally threaded as at 18 adjacent the open end 16 thereof for threaded engagement with "ice threaded portion 12 of the recess of article 13. The switch 10 has a heat absorbing head 19 which is urged in one direction out of the open'end 16 of the switch 10 by pressure means such as 20. Stop means 21, 22 assure limited movement of the heat absorbing head 19 out of the free end 16 of the switch responsive to the pressure means 20. The switch 10 may be connected to a circuit for an electrical component such as, for example, a warnin li ht or other device to be controlled by the switch 141 responsive to thermal changes of article 13; binding post 23 on the other end of the switch connecting with said circuit. Contacts 48, 49 of leaves 24, 25 are provided within the switch, connected respectively to the heat absorbing head 19 and the binding post 23. A Wire 26 connects binding post 23 with disc 27 to which one end of leaf 25 is secured directly or through the medium of a mounting bar 28 containing an adjusting screw 29 for thus predetermining the relative spacing (as 30, Fig. 1) of the leaves 24, 25.

In the preferred form of the invention as illustrated in the drawings, the shell 31 is proportioned to freely slidably move within the axial opening 17 of the outer casing 11. The shell and easing have complementarily shouldered portions 21, '22 and the parts are so proportioned that even when the outer casing 11 is fully threaded within the threaded portion 12 of the article 13, and heat absorbing head 19, which is tapered to conform to the countersunk inner end 14, of recess 12, is in direct contact with said inner end 14, the shouldered portion 22 of the shell 31 will be spaced from the shouldered portion 21 on, the outer casing 11. Thus the heat absorbing head 19 of the shell 31 will be maintained at all times in pressure contact with the inner end 14 of the recess 12 of the article 13. The end of the shell is preferably marginally flanged as at 32 to define a shouldered portion within which the disc 33 and against which the head 19 may be secured. The head 19 may be formed of a material such as brass which will rapidly conduct heat and may be silver brazed or otherwise secured to the marginal flange 32 of the inner shell 31. Leaf 25 may be made of a good high temperature spring material such as Inconel X and the other leaf 24 of a thermostatic material so as to flex and close upon the leaf 25 (on heating the article 13 to a predetermined temperature). Screw 29 may be adjusted through an aperture 34 in the shell 31 and said aperture may be sealed after adjustment has been made by any suitable seal 35. The end 36 of the shell 31 opposite the head 19 thereof may be closed as for example, by forming said end shouldered as at 37 and positioning a metal ring 38 in said shouldered end, then positioning a mica washer 39 on said metal ring 38, then positioning the disc 27 to which the bar 28 is secured over the washer 39 and then positioning a second mica washer 40 over the disc 27, a final metal ring 41 being positioned over the mica washer 40 and the end of the shell 31 formed in over ring 41. A metal cap 42 may be secured to the formed end of the inner shell 31 and a glass disc 44 fused thereto, flexible wire 26 passing in sealed relation through brazed seal 51 in tube 50 in glass disc 44. A closure cap 45 may be secured to the end of the outer casing 11 opposite the free open end 16 thereof as by welding the same thereto at 46 (Fig. l) and the binding post 23 may be fused to the cap 45 through a glass ring 47. The terms glass, metal, mica, threaded and the like as used herein are illustrative only; other forms well known in this art and useful for the purpose are embraced within said terms.

We claim:

1. In a switch actuated responsive to thermal changes in an article to which said switch is attached, said article having a threaded recess terminating in an inner end, said recess extending inwardly of a surface of said article, said switch comprising an elongated outer casing, open at one end, and having an axial internal opening extending to said open end of the casing, an externally threaded portion on said casing adjacent and spaced from said open end thereof, an elongated inner shell freely slidably positioned within the outer casing, means engaging the inner shell and outer casing and normally urging one end of said inner shell out of the casing, means limiting the extent of movement of the shell, a heat absorbing head secured to said one end of the casing, and proportioned to conform to the inner end portion of the recess for contact seating thereagainst under pressure of said urging means, and thermally actuated switch elements in said shell connected to said heat-absorbing head of the shell, whereby the threaded end of said casing may be engaged with the threaded recess of said article to position the heat-absorbing head of the inner shell against the inner end portion of the article recess and on further threading-of the switch into the recess the head of the shell will retract slightly in the casing, against said urging means.

2. In a switch set forth in claim 1, complementary stop means on the shell and casing to limit the sliding movement of the shell responsive to the urging means.

the shell responsive to said urging means beyond a limited extent.

4. In a switch as set forth in claim 1, said thermally actuated switch elements comprising a thermostatic contact arm so connected to said heat absorbing head of the shell, and a contact arm fixed to the opposite end of the shell.

5. In a switch as set forth in claim 1, the end of the outer casing opposite the open end thereof being closed and said urging means comprising a spring bearing at opposite ends against the said closed end of the casing and said shell.

6. In a switch as set forth in claim 4, a lead wire sealed to the opposite end of the shell, a binding post secured to said closed end of the casing, said lead wire being secured to said opposite end of the shell and to the binding post, said thermally actuated switch elements including the lead wire.

7. In a switch as set forth in claim 6, adjustment means engaging one of said contact arms for adjusting the normal position thereof relative to the other contact arm.

References Cited in the file of this patent UNITED STATES PATENTS Day Jan. 12, 1954 

